[TRNSYS-users] Type 401 input

[elena.bee at libero.it]

Hi everyone! 
I'm modeling a heating system with an air to water heat pump, using type 401. 
Two inputs required for this type are condenser mass flow and evaporator mass 
flow. The first one is the mass flow of water circulating in my heating system 
but i can't understand why it ask me the second, since the eveporator exchanges 
heat with external air (there's no air mass flow). Can someone help me please? 
Thanks in advance
Regards, Elena